1. Field of the Invention
The present invention relates generally to the fabrication of semiconductor integrated circuits and, more particularly, to a method of fabricating semiconductor integrated circuits with improved yields.
2. Description of the Prior Art
The manufacture of integrated circuits requires high cost equipments, clean rooms and cutting edge process technologies. To amortize this high capital expenditure, it is necessary to increase the yields as much as possible, but with costs for quality control and process realization at an acceptable level.
Spin-on coated materials such as photoresists, spin-on glasses and some low-k materials are frequently used in this art. The spin-on material such as photoresist is dispensed onto a spinning wafer from its center. Particles deposited on the wafer surface usually result in sectorial defect areas on the wafer, which are typically inspected by visual means. For example, an operator places the wafer under a microscope and inspects the wafer surface to identify the defect areas. Such manual process is done off-line, and is thus time consuming.
U.S. Pat. No. 6,507,394 discloses a method of inspecting the surface of a semiconductor device. The disclosed optical inspection system for detecting defects on the surface of a semiconductor wafer requires two light sources and two light receivers mounted as a common assembly, which is rotated such that two curtains of light and corresponding linear photosensor arrays circularly scan the wafer surface. The reflected light is analyzed to determine the presence of surface defects. Marks applied to the wafer surface provide amplitude and timing references used to adjust and synchronize the analyzed signals.
It is disadvantageous that according to this patent the wafer has to be removed from the wafer stage of a spin coat system and then placed on a conveyor driven by rollers, which moves the wafer linearly. A motor is also required to rotate the sensor assembly. Besides, such inspection system is complicated and is not particularly effective in detecting the above-mentioned sectorial defect areas on the wafer.